The overall objective of this proposal is to understand the pathophysiology of the autosomal dominant transthyretin (prealbumin) amyloidoses. These diseases, which affect a number of kindreds worldwide and with large families in the United States are manifest as peripheral neuropathy, nephropathy and cardiomyopathy. They are late-onset diseases but are associated with high degrees of morbidity and mortality. Several of these syndromes have been found to be associated with mutations in the gene for transthyretin (prealbumin) which result in single amino acid substitutions. How these mutations lead to amyloid fibril formation and disease expression is not known. These studies will investigate the pathophysiology of the process leading to clinical disease and will test the hypothesis that the single amino acid substitutions associated with amyloidosis cause 1) changes in metabolism of the variant molecule compared to normal and 2) identifiable changes in the secondary and tertiary structures of the variant protein. It is proposed that this change in structure and its metabolic consequences lead directly to amyloid fibril formation and then the clinical disease. These aims will be accomplished by synthesizing recombinant variant transthyretin proteins in order to have variants separated from normal transthyretin. This will allow evaluation of the metabolism of the amyloid precursor proteins. It will also allow study of the tertiary structure of the variant transthyretin molecules. Crystallographic data already obtained on one mutant transthyretin (Met-30) which was obtained from homozygous individuals' plasma has shown that this method is feasible and practical. These data will be compared to normal transthyretin and a model formulated to explain the factors involved in polymerization to form amyloid fibrils. Accomplishment of these specific aims will allow identification of crucial factors in the pathophysiology of amyloid fibril formation and may lead to methods to prevent amyloid formation and therefore disease expression.